Detachable drilling bit



March 11, 1952 T. M. WAT'ERLAND 2,588,782

DETACHABLE DRILLING BIT Filed March 3, 1947 Patented Mar. 11, 1952 DETACHABLE DRILLING BIT Tilmer Manville Waterland, Britannia Beach, British Columbia, Canada Application March 3, 1947, Serial No. 732,097

4 Claims.

This invention relates to drill bits, particularly to bits which are adapted for use in exceptionally hard and tough ground. The form of the parts of a drill bit which come into direct contact with the material through which the drill hole is driven should be such that a reasonably rapid rate of drilling may beattained in material of a given character, that the bit should not be susceptible to chipping-or breakage, and that it should be capable of use for comparatively long periods without either serious loss of drilling efficiency or a tendency to bind in the drill hole or give the hole drilled a shape such that a fresh bit tends to bind in it.

The types of drill bits now used all have wings with sharply pointed cutting edges and reaming faces which slope inwards from the corners of the wings at angles of about 5 to 7' to the axis of the bit, the angle of slope being known as the reaming angle. From the upper ends of the reaming faces, 1. e. the ends remote from the cutting edges, the wings taper inwards to merge with the shank of the bit, the taper angle being generally from about 14 to 20 to the axis of the bit.

Various reaming angles have been proposed and experimented with. The smaller the reaming angle, that is, the more nearly the reaming faces are parallel to the axis of the bit, the slower will be the loss of gauge of the bit, i. e. the reduction of its diameter during drilling. On the other hand, if a corner of the wing breaks off the reaming angle is more likely to be reversed, i. e. the reaming faces are more likely to slope inwards towards the cutting faces rather than away from them. However, though the consequences of corner breakage are more serious with a small duced, and the rate of gauge reduction thus increased. It was in order to offset this that the tapered portions backing up the wings were provided, so that when a wing corner broke and the reaming face tended to wear down quickly it would wear into the tapered portion and gradually increase in length and thus in area, so that the rate of wearing down was reduced. However, this increase in length took place also during normal Wear, with the result that conventional bits turned less freely the more they were worn, but this difiiculty had to be put up with for the sake of avoiding the more serious difficulty of rapid gauge loss.

It was proposed many years ago that the outer ends of the cutting edges of the wings of a drill bit should be flattened so as to reduce the amount of wear in these parts. The proposal, however, was never taken up in practice, and the wings of all drill bits today have sharp cutting edges.

I have discovered that the flattening of the outer ends of the cutting edges of the wings has an effect far more important than that of mere day standard bits in such a way as to increase the than with a larger reaming angle, the likelihood of corner breakage decreases with the reaming angle. In spite of this, however, the likelihood of corner breakage was in any event so great with the usual sharp-edged wings that it was more important to reduce the consequences of a break if it occurred than to decrease its likelihood, and consequently, though greater reaming angles would increase the likelihood of wing corner breakage, the reaming angle adopted as standard in practically all bits was between 5 and 7.

For a bit to be used in any particular type of ground there is an optimum reaming face area. If the area is too great the bit will not turn freely enough, and if it is too small the bit will lose gauge too quickly. Of these two difliculties the second is generally the more serious. In the standard bits with sharp-edged wings the incidence of wing corner breakage -is high. If the wing corners break the reaming face area is reaverage life of the bit and the average drilling speed by still further reducing the incidence of wing corner breakage, reducing the area of the reaming faces and keeping it substantially constant throughout the normal life of the bit, and at the same time reducing the average rate of gauge reduction. I achieve these results by providing a bit in which the cutting edges of the wings are flattened at least at their outer ends, the reaming angle of the reaming faces is not over 3, and the reaming faces terminate at their upper ends in shoulders sloping inwards at sharp angles to the axis of the bit.

The invention will be described in more detail by reference to the attached figures, which illustrate two embodiments of it, and in which Figures 1, 2 and 3 are respectively a side elevation, a longitudinal section and a bottom plan view of a four-wing detachable drill bit embodying the invention, and

Figures 4, 5 and 6 are respectively a side elevation, a longitudinal section and a bottom plan view of a three-wing detachable drill bit embodying the invention.

The bit of Figures 1-3 has four wings l0. Each of these has a cutting edge I I which is flattened, as appears from Figures 1-3, throughout its length. The peripheral faces [2 of the wings constitute reaming faces and slope inwards from the corners I3 of the wings at angles of 2 to the axis of the bit. They terminate at their upper ends I4 in shoulders l5 which slope inwards at sharp angles of about 45 to the axis of the bit.

The flattened cutting edge l l of the wings may advantageously be fromone-fifth to one-tenth of the width of the wings at the upper ends 14 of the reaming faces 12. Generally the width of the flattened cutting edge is about three thirtyseconds of an inch.

Although the slope of the reaming faces is preferably about 2, it may be as great as about 3, but should not exceed this. 7

The shoulders 15 are preferably formed at point such that the length of the reaming faces is substantially the same as the length of the reaming faces in standard bits, this length varying generally from to and they are preferably about deep. The result is that the diameter of the bit must be worn down by one-quarter of an inch before any appreciable increase in length of the reaming face occurs. It has been found that standard bits having the usual width of wings and reaming faces of an initial length of to usually began to bind when the reaming face lengthened to about /3. The slope of the shoulders is not critical. It should be sharp enough that the reaming faces do not substantially lengthen as the bit loses gauge, but the shoulders should preferably not be square in order to avoid the possibility of chipping. The slope is preferably about 45.

It has been found possible as a result of the new construction to make the Wings of less width circumferentially of the bit than in the standard type. A series of tests under very severe conditions showed that with the new construction it was possible to use a wing of a thickness of as against a wing thickness of in the standard type of bit. This appears to be principally the result of the stronger wing corner resulting from a combination of the flattened cutting edge and the steep reaming face.

The three-wing bit shown in Figures 4-6 is made in the same way as the four-wing bit of Figures l-3, and differs from the latter only in the number of wings.

This application is a continuation-in-part of application Serial No. 614,477 filed September 5, 1945, now abandoned.

I claim:

1. A percussive drill bit comprising in combination, a plurality of wings extending radially outwards from the axis of the bit, a cutting edge on each wing which extends transversely to the axis of the bit, said cutting edges being flattened at least at their outer ends the ratio of the widths of each wing and the flattened portion of its cutting edge lying in the range of 5:1 to 10:1, a peripheral end surface on each Wing constituting a reaming face, each said reaming face sloping inwardly away from said cutting edges at an angle of 2 to 3 to the bit axis, and a shoulder which slopes steeply towards the axis of the bit from the upper end of each reaming face.

2. A percussive drill bit as claimed in claim 1 in which the cutting edges are flattened throughout their length.

3. A percussive drill bit as claimed in claim 1 in which each shoulder slopes at an angle of approximately 45 to the axis of the bit.

4. A percussive drill bit comprising in combination, a substantially cylindrical bit body, a socket formed in the upper portion of said body, a plurality of V-shaped wings extending radially outwards from the lowest portion of said body, said wings terminating in arcuate peripheral end reaming surfaces, flattened impact cutting surfaces formed on the apex of each wing and extending transversely to the axis of the bit, the ratio of the widths of a wing and the flat portion of its cutting edge lying in the range of 5:1 and 10:1, said reaming surfaces sloping upwards and inwards from said flattened cutting surface at an angle of approximately 2 to the axis of the 1 bit, and shoulders above said reaming surfaces extending from the top edge of each reaming surface to the external surface of said socket and sloping inwards at an angle of substantially 45 with respect to the vertical axis of the bit.

TILMER MANVILLE WATERLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number A Name Date 1,036,673 Meguire Aug. 27, 1912 1,094,063 Forbes Apr. 21, 1914 1,388,792 Bernay Aug. 23, 1921 1,913,267 Deyo June 6, 1933 1,931,590 Sanderson Oct. 24, 1933 2,266,572 Siebert et 'al. Dec. 16, 1941 

